Mechanical or chemical-mechanical planarizing processes (CMP) are used to form a substantially flat surface on microelectronic substrates such as semiconductor wafers used in the fabrication of semiconductor devices. FIG. 1 shows a planarizing apparatus 100 comprising a planarizing medium 102 stretched over a platen 104 and a substrate holder 106 that holds the substrate 108. The substrate holder presses the substrate against the planarizing medium, translates and/or rotates it to planarize the substrate. The platen having the planarizing medium thereon may also be rotated relative to the substrate during planarization.
The planarizing medium comprises, for example, a fixed abrasive web. A fixed abrasive comprises abrasive particles embedded within a suspension medium. In one embodiment, the planarizing apparatus has a plurality of rollers to supply, guide and collect the web-format planarizing medium. The rollers include a supply roller 110 to supply fresh or un-used portions of the web and a take-up roller 112 to collect worn or used portions of the web. The web is advanced across the platen such that a fresh portion of the web is introduced into the planarizing region 114 and a worn portion of the web is collected at the take-up roller 112.
One problem associated with fixed abrasive planarizing processes is that the introduction of fresh planarizing material may generate defects on the surface of the substrate. Prior to usage, the surface of fresh planarizing material comprises a highly non-uniform surface topography that may introduce defects such as scratches or gouges on the substrates. The non-uniformity of the planarizing material surface also leads to high unpredictability in the rate at which material is removed from the surface of the substrate. Additionally, the upper surfaces of the posts on the fresh portions of the web are very small, leading to high local pressures between the posts and the substrate which result in scratches and indentations on the substrate. The high rate of defect generation disadvantageously results In loss of yield of operable devices or dies that can be cut or formed from the substrates and lowers the efficiency of the fabrication process.
Hence, it Is desirable to provide a method to prepare the surface of the planarizing web material for use in chemical mechanical planarization processes, in order to increase the efficiency and yield of the manufacturing process.
The present invention relates to planarization of microelectronic substrates. More particularly, the invention relates to a method and apparatus of preparing web media for planarizing substrates. In accordance with the invention, a planarizing web having a planarizing region and preparing region defined thereon is provided, wherein at least one portion of the preparing region is outside the planarizing region. In one embodiment, the preparing region is outside the planarizing region. In another embodiment, the outer portion of the preparing region is outside the planarizing region. The planarizing web Is advanced to move one portion of the web out of the planarizing region and another portion of the web into the planarizing region to replace the worn portion.